Pink- and orange-pigmented Planctomycetes produce saproxanthin-type carotenoids including a rare C45 carotenoid
2019
Kallscheuer, N. | Moreira, C. | Airs, R. | Llewellyn, C.A. | Wiegand, S. | Jogler, C. | Lage, O.M. | Centro Interdisciplinar de Investigação Marinha e Ambiental
Planctomycetes are ubiquitous and environmentally important Gram‐negative aquatic bacteria with key roles in global carbon and nitrogen cycles. Many planctomycetal species have a pink or orange colour and have been suggested to produce carotenoids. Potential applications as food colorants or anti‐oxidants have been proposed. Hitherto, the planctomycetal metabolism is largely unexplored and the strain pigmentation has not been explored. For a holistic view of the complex planctomycetal physiology, we analysed carotenoid profiles of the pink‐pigmented strain Rhodopirellula rubra LF2T and of the orange strain Rubinisphaera brasiliensis Gr7. During LC–MS/MS analysis of culture extracts, we could identify three saproxanthin‐type carotenoids including a rare C45 carotenoid. These compounds, saproxanthin, dehydroflexixanthin and 2′‐isopentenyldehydrosaproxanthin, derive from the common carotenoid precursor lycopene and are characterized by related end groups, namely a 3‐hydroxylated β‐carotene‐like cyclohexene ring as one end group and simple hydration on the other end of the molecule. Based on the observed molecule structure we present putative pathways for their biosynthesis. Results support Planctomycetes as a promising, yet mostly untapped source of carotenoids.
Show more [+] Less [-]This research was partially supported by the Strategic Funding UID/Multi/04423/2019 through national funds pro- vided by FCT - Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020 and by the German Research Foundation (DFG), Grant KA 4967/1-1, Project Number 405562673.
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